Ironbridge is great - we spent a couple of days there and visited all the museums, had a boat trip on the Severn and tried pork pies from the shop at the end of the bridge. We were there because a GS needed to know about the Industrial Revolution but so enjoyed it we'll certainly return soon.
I'm biased about Brum, there's so much going on here these days and also recommend the Black Country Museum. Loads to see and do in and around Warwick and Stratford too of course. You've had some great suggestions above from other posters. Have a lovely time when you come to the West Midlands!
If you go to Cadbury World don't miss Selly Manor and Minworth Greaves - Tudor buildings on the corner of Bournville Green. As well as the Birmingham Botanical Garden, the University Botanic Garden, Winterbourne, which is quite close, is also well worth a visit.